Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.82	6.414%	$186.033	$186.03	$186.05	$186.00
Purchase #2	$199.33	11.809%	$222.8689	$222.87	$222.85	$222.90
Purchase #3	$89.47	13.397%	$101.4563	$101.46	$101.45	$101.50
Purchase #4	$37.60	7.165%	$40.294	$40.29	$40.30	$40.30
Purchase #5	$209.47	4.249%	$218.3704	$218.37	$218.35	$218.40
Purchase #6	$102.85	3.158%	$106.098	$106.10	$106.10	$106.10
Purchase #7	$147.82	5.730%	$156.2901	$156.29	$156.30	$156.30
7 purchase totals =	$961.36		$1,031.4107	$1,031.41	$1,031.40	$1,031.50